1. Technical Field
The present invention relates to a piezoelectric element including a piezoelectric layer made of a piezoelectric material and electrodes, and to a liquid ejecting head and a liquid ejecting apparatus that each include the piezoelectric element and that eject droplets from nozzle apertures. The invention also relates to a method for evaluating the piezoelectric layer.
2. Related Art
Ink jet recording heads are a typical type of liquid ejecting head. For example, an ink jet recording head includes a vibration plate defining a part of a pressure generating chamber communicating with nozzles through which ink droplets are discharged. In the ink jet recording head, a piezoelectric element deforms a vibration plate to apply a pressure to the ink in the pressure generating chamber, thereby discharging ink droplets through the nozzles. Some of the piezoelectric elements used in ink jet recording heads have a structure in which a piezoelectric layer (piezoelectric film) made of a piezoelectric material capable of electromechanical conversion, such as a crystallized dielectric material, is disposed between two electrodes.
The piezoelectric material used for forming the piezoelectric layer of such a piezoelectric element is required to have high piezoelectric properties, and a typical example of the piezoelectric material is lead zirconate titanate (PZT) (see JP-A-2001-223404 and JP-A-2001-19543). In addition, in view of environmental issues, it is desirable that the piezoelectric material contain no lead or a reduced amount of lead. For example, JPA-2007-287745 discloses a lead-free piezoelectric material containing Bi, Ba, Fe and Ti.
Although various types of piezoelectric material are used for the piezoelectric layer, cracks can occur in the piezoelectric layer of any type of piezoelectric material. This problem can arise not only in liquid ejecting heads, a representative example of which is an ink jet recording head, but also in piezoelectric elements used for other applications.